1. Field of the Invention
The present embodiments provided herein relate generally to horticultural, plant breeding and plant genetics.
2. Description of Related Art
Ornamental plants such as begonias, geraniums, impatiens and poinsettias comprise a large and profitable market both in the U.S. and abroad. The poinsettia (Euphorbia pulcherrima Willd.), for example, is a member of the family Euphorbiaceae which is very popular as a live ornamental decoration. The highly prized blooms of these plants, known as bracts, are not true flowers, but rather modified leaves that form large flower-like arrays. Popular ornamental varieties produce bracts in a variety of brilliant colors such as red, orange, white, yellow and pink.
Production of quality ornamental poinsettias can be difficult and labor intensive. In the wild, plants produce a single bloom from a tall (up to ten foot) vertical stem. On the other hand, ornamental poinsettias preferably have a mounded bushy habit with multiple lateral branches. To produce such plants, the growth tip of the poinsettia is mechanically removed during the vegetative growth phase by a process known as pinching. Such pinching stimulates lateral branching and can be used to control the size of the resulting plant. Alternatively or additionally, lateral branching can be stimulated by exposure of the plants to a branching agent, such as the poinsettia, branch-inducing phytoplasma (Lee et al. 1998). For instance, plants can be inoculated with phytoplasma by grafting of phytoplasma-infected plant tissues. All of the above methods, however, require substantial labor and therefore result in increased production cost.